Overspeed preventing mechanism



Oct. l0, 1944. D. J. coNANT 2,359,899

OVERSPEED P-REVENTING MECHNISM Filed Feb. 18, 1945 Y v/aJvo/v/w 25 24 5 27 gam/h.

Patented Oct. 10, 1944 y 2,359,899 ovansraan raEvENrmG MEcnANIsM David J. Conant, Cleveland Heights, Ohio, as-

signor to Jack & Heintl, Inc., Bedford, Ohio, a

corporation of Ohio Application February 18 1943, Serial No. 476,342 a claims. (o1. zmpso) The present invention relates to a novel governor operated circuit breaker to prevent overspeeding of an electric motor or motor operated device.

In energizing inertia starters on aircraft engines it is customary where a source of power is available to employ a portable external electric energizer to accelerate the ywheel in the starter to a high speed. Such energizers are made sufciently powerful for the largest engines and starters under adverse conditions, and are liable to overspeed, particularly when applied to smaller engines and starters. The object of the present invention is to provide a. rugged and reliable circuit breaker responsive to motor speed to prevent -overspeeding of an energizer motor.

In accordance with the patent statutes a preferred embodiment of the invention is illustrated in the accompanying drawing in which:

Figure 1 is a fragmentary sectional view through an energizer of the type referred to, showing the governor and circuit breaker of the present invention in their relation to the motor of the energizer; and

Figure 2 is anend view, looking from the left in Figure 1, with the switch housing broken away to show the operating parts therein.

The numeral I refers to an energizer housing containing a motor having an armature 2 carried at one end in a rear bearing 3. The bearing 3 is mounted in a bearing housing 4 which also accommodates a governor for operating a circuit breaker. The governor comprises a pair of weights 5 pivotally mounted at 6 on a U-shaped member 1 on the end of the armature shaft 8.

Each Weight 5 is provided with a. bell crank arm 9 adapted to bear against a head I0 on an axially disposed pin II. The pin II- is rotatably carried in a plunger I2 which is mounted for axial and rotative movements in the end of bearing housing 4. The plunger I2 is biased inwardly of bearing housing 4 by means of a spring I3 abutting the flange I4, the inward movement being limited by snap ring I5.

The circuit breaker is designated generally by the numeral and is mounted on a portion 2| of the energizer adjacent the bearing housing 4. The circuit breaker contains two terminal posts 22 and spring contact fingers 23 in circuit with a main line to the energizer motor, this circuit Abeing normally maintained through an annular conductor band 24 on a plunger 25. The plunger 25 has an enlarged hollow portion 26 slidable in a guide 21, and a reduced extension 23 slidable in a guide 23. A compression spring housed within the hollow portion 26 serves to bias the plunger 25 to the right as viewed in Figure 2 with the shoulder 3l of enlarged portion 26 abutting a release lever 32 pivoted on a member 33. A torsion spring 34 serves to bias lever 32 against the plunger 25. The plunger and contacts are preferably contained within a two part housing comprising a base 35 having means of attachment to the portion 2| of the energizer, and a cover 36 having a post or boss 31 carrying the member 33 externally of said cover. One end of the lever 32 projects through an opening in cover 36 to engage the plunger 25 in the manner of a locking sear, and the other end has an angle` portion 38 disposed for engagement by plunger I2 in the governor.

The various parts normally assume the positions shown in full lines, but are operative to open the motor circuit upon overspeeding of the motor. The governor is designed so that at a predetermined critical speed the weights 5 are effective to move the bell crank arms 3 against the force of spring I3, to move plunger I2 outwardly. This motion is transmitted to the release lever 32 which is thereby brought to approximately the broken line position in Figure 1, causing the inner end of lever 32 to clear the shoulder 3I on plunger 25. Plunger 25 then snaps to the right in Figure 2, carrying conductor band 24 beyond the contact ilngers 23 and opening the circuit to the motor. The openV circuit position of plunger 25 is indicated by broken lines in Figure 2, the shoulder 3 I `having been stopped by guide 29.

The projecting end 28l of plunger 2-5 constitutes a reset button and is disposed to project outside the energizer housing I in the open circuit position. After a circuit breaking operation the governor plunger I2 will be again retracted as the motor slows down, and spring 34 will cause the inner end ofrelease arm 32 to move into contact with plunger 25. Extension 23 may then bemanually depressed until lever 32 snaps behind shoulder 3l to hold the conductor band 24 again under contact fingers 33 to reestablish the motor circuit. If the motor again overspeeds, the cycle' o f events to open the circuit will be repeated, and the circuit breaker may be again reset thereafter. By virtue of the annular contact 24 the wear may be distributed therearound to greatly prolong the life of the circuit breaker, thereby reducing the weight and size of the parts to pro,- duce a prescribed number of'operations before failure.

Various changes and modifications will occur $9 hOSe skilled in the art. andit is to be understood that the invention is to be limited only by the scope of the prior art and the appended claims.

I claim:

l. Overspeed preventing mechanism for a motor driven shaft comprising a bearing housing receiving an end of said shaft and its associated bearing therein, a pair of governor weights within said housing and rotatable with said shaft, a pin axially movable by said weights, a hollow plunger receiving said pin therein, said plunger being journalled in said bearing housing and projecting therethrough, a flange on said plunger within said housing, a compression spring surrounding said plunger and bearing against said bearing housing and said ange to retract said plunger, a locking scar lever engageable gradually by said plunger to release a spring biased switch plunger by movement at right angles thereto, and a bridging contact on said switch plunger adapted to normally bridge a pair of spring contact lingers to close a circuit for energizing said motor and adapted to move away from said contact fin-gers with a snap action to open said circuit when released by said lever.

2. Overspeed preventing mechanism for a rotating shaft comprising a governor plunger adapted to be extended from a rest position in response to overspeeding of said shaft, a circuit breaker for controlling a motivating power supply ior rotating said shaft, said circuit breaker comprising a pair of spaced contacts, a switch plunger movable between said contacts, a bridging contact on said plunger, a locking sear lever for holding'said plunger in bridging relation with said pair of contacts, and spring means urging said plunger to open circuit position, said lever being arranged for gradual actuation by said governor plunger to move at right angles to said switch plunger to release said switch plunger to move said bridging contact away from said spaced contacts with a snap acting movement at a predetermined speed of said shaft.

3. A circuit breaker adapted for actuation by a governor to prevent overspeeding of a power driven member comprising a housing, a pair of aligned guides in said housing, a cylindrical plunger slidable in said guides, a pair of contact fingers engageable with said plunger, an annular contact bridging element on said plunger, a hollow-portion in said plunger, a spring in said hollow portion to bias said plunger to open circuit position, a shoulder on said plunger adapted to abut one of said guides to limit the movement of said plunger in circuit opening position, a portion of said plunger extending through said housying to serve as a manual resetting button, and a locking sear lever pivotally mounted on said housing for movement at right angles to said plunger, one end of said lever extending within said housing to engage said shoulder to hold said plunger normally in closed circuit position and one end of said lever extending outwardly from said housing for gradual actuation by said governor to release said plunger for a snap acting circuit opening movement.

DAVE) J. CONANT. 

